Honing Liners?

[jack biscuit 0]

Got two projects to do on the horizon, blown head gasket on my 1.6 (the root cause of my mystery 'ignition' problem), and.. Doing a rebuild on a 1.9

 

The head gasket i've got no real thoughts about or apprehension but if anyone has a bit of advice or any pointers regarding a bad experience i'd appreciate hearing it!

 

However, the 1.9 had been in storage for a while, bagged up.. i've come to inspect it and some kind soul has put their finger through the top.. allowing some moisture to get at the one cylinder and now it has a little very light corrosion in there.

 

The question is has anyone got any experience of having a liner honed? (I've never done it)

 

Is it feasible to do this? (I know it can be done, just is it really an option>?)

 

Thanks all and anyone!

[205007 12]

its not that hard to do with the correct tool, the only ball ache is putting the piston rings back in properly which again you need a tool for

 

if you havnt done it before id say get someone who knows what they are doing to help or you could f*** your liner up and you wont know untill you have boxed it all back up!

[j_turnell 134 3 Cars]

The liners should be honed on a rebuild anyway. Depends how bad it is may get away with some wd-40 and a cloth to clean the corrosion off. With regarding honing, you can by a drill attachment that has prongs on that you put in the liner and with some brake fluid spin it around covering the whole liner evenly, there shouldnt be a lip on the liner, if there is it may be past it and youll need new ones. It effectively de glazes the bores.

 

When putting the pistons back in you can buy a cylindrical clamp which holds the rings allowing you to push the piston in the liner. Sure there are lots of other options but thats what i use and have no problems.

[petert 554]

its not that hard to do with the correct tool,

 

It's actually very hard to do correctly. The liner has to be held in a fixture that simulates the load of the head bolts compressing it. If you hone it unloaded, it's guarenteed to be out of round.

[PumaRacing 1]

It's actually very hard to do correctly. The liner has to be held in a fixture that simulates the load of the head bolts compressing it. If you hone it unloaded, it's guarenteed to be out of round.

 

You've said this before in another thread. I still fail to see how a vertical clamping load can make a round tube go out of round to any material extent. Do you have any tests or measurements to back this up or is this just conjecture?

 

As it happens I made a 205 liner clamping fixture for honing liners some time ago. In fact possibly the best such honing fixture it's possible to devise because I took an actual 205 head, removed the guides and seat inserts and bored right through it at 84mm in each liner position so I can clamp all 4 liners in a scrap block with a real head on top of them. If that doesn't simulate the actual installed loads I'm not sure what will.

 

My bore gauge reads to 1 tenth of a thousandth of an inch so if I clamp a liner in this fixture and measure it for out of round both clamped and unclamped will you take this as an accurate test of your hypothesis?

[petert 554]

That would be an excellent test and I look forward to hearing of the results. You've obviously taking torque plate honing seriously. It's not a round tube and thus there lies the problem.

 

It's more than likely that most liners are slightly out of round (up to a few tenths) from the factory. After seeing the results of an Mi16 liner that a "pro" tried to bore to 83.50mm, which ended up 0.25mm out of round, I only use one place now - Baker Precision Engines in Molong, NSW. It's a four hour drive west from Sydney and worth the effort. They're aircraft certified and take their work very seriously. Both the BMW and Peugeot Supertourer teams tuned their engines on Bakers dyno (they both made 295hp @ 8500!).

Edited February 25, 2006 by petert

[DrSeuss 0]

doesn't the fact that liners aren't tubes, but have a variation in wall thickness have an effect? Do the liners ever touch in an engine?

[PumaRacing 1]

1 thou ovality on brand new factory bores and liners isn't unusual. I personally don't think it makes as much difference as people claim. Piston rings adapt to oval bore shapes quite happily. After all it's only about 1 thou in 3500 thou in an average engine.

[M3Evo 0]

So (excuse my ignorance) do they use these torque plates at the factory when the bores are originally cut and honed?

[PumaRacing 1]

So (excuse my ignorance) do they use these torque plates at the factory when the bores are originally cut and honed?

 

Yes. All OE manufacturers use torque plates before honing, hand porting to finish the cylinder heads to extract the last few bhp and a full dyno calibration in case tolerances leave the standard map settings a bit rich or lean.

[M3Evo 0]

Thought not

[petert 554]

I personally don't think it makes as much difference as people claim. Piston rings adapt to oval bore shapes quite happily.

 

That's a relief then. I won't have to drive to Molong anymore.

[Mandic 0]

You've said this before in another thread. I still fail to see how a vertical clamping load can make a round tube go out of round to any material extent. Do you have any tests or measurements to back this up or is this just conjecture?

 

As it happens I made a 205 liner clamping fixture for honing liners some time ago. In fact possibly the best such honing fixture it's possible to devise because I took an actual 205 head, removed the guides and seat inserts and bored right through it at 84mm in each liner position so I can clamp all 4 liners in a scrap block with a real head on top of them. If that doesn't simulate the actual installed loads I'm not sure what will.

 

My bore gauge reads to 1 tenth of a thousandth of an inch so if I clamp a liner in this fixture and measure it for out of round both clamped and unclamped will you take this as an accurate test of your hypothesis?

 

I had a word the other day with a guy who knows a thing or two about engines and he stated the exact same thing!

 

He said that best tuners always use this "drilled" head method.

 

Cheers

 

Ziga

[Mattsav 1]

We had a nightmare boring liners to 84mm. They were clamped in a universal liner fixture and bored/honed. Took them out and they were all over the place. Put them in a block and they were still distorted.

 

We've now made a steel deck plate and bore & hone the liners with this fitted to a block (with a gasket fitted).

They still distort over when taken out but return to within a couple of tenths when fitted into a block which is acceptable.

[Beastie 1]

Can we make a distinction between honing and glaze busting here? I suspect that what Puma, Mattsav PeterT etc are referring to is genuinely honing. Many people confuse this with glaze busting which produces a similar looking finish on a cylinder bore. A glaze buster is (usually) a three - pronged spring loaded tool which fits in an electric drill and produces an nice looking cross hatched finish in the bore. It's a great DIY tool and is really useful when you want new rings to bed in properly. It removes relatively little metal and simply follows the shape of the existing bore. It's no good at all for finishing freshly rebored surfaces because it does tend to "smooth over" the machined surface and leave minute hidden defects underneath.

 

A hone is a precision piece of equipment which removes more metal than a glaze buster. To the naked eye it leaves a very similar finish to a glaze buster. When finishing a rebored surface it removes enough metal to provide a long lasting and correct finish for new piston rings. It is for true honing that deck plates are used. If you are doing a DIY engine rebuild and are using a glaze buster to titivate your cylinder bores then I really don't see the point of using deck plates.

 

I'd be interested in a proper test of the merits of deck plates when using a hone (not a glaze buster) too. However I don't think that readings in tenths are of very much scientific value unless taken in a temperature controlled laboratory?

[jack biscuit 0]

Yes! Distinctions!

 

Heh, This has started going further than what i imagined, but to my eyes this is no bad thing.

I am a novice with peugeot engines, and i'm no machinist..

 

As regards my liner, i'm pretty sure it will clean up.. But i am considering all possibilities, especially as the 1.9 lump is a toy project. (*)

 

Using an bored out old head on the block before HONING or REBORING makes perfect sense to me, previously i'd heard of using a thick steel plate to do this, at least on cast iron blocks, but why go to that hassle of having one made up with so many scrapped heads around i don't know..

 

(*) all possibilities include increasing capacity, but bore not stroke (Not planning on messing with cranks and conrod lengths). As for requiring a liner to be honed to a slight oversize, what sort of price should i expect to pay for a good job? and if i wish to build a larger engine, what options present themselves with the Xu? I know there's larger bore and piston combinations out of the box, fine and all, but what pistons can be used with a overbored liner (Not my favorite idea, but an option)

 

Verbose and vague i know, but some of you guys like typing and this should give some of you another opportunity to lock horns and argue.

 

Seems some of you love this! (and i get to pick up the pieces of knowlege left scattered on the floor)

 

Thanks for your responses thus far good people..

[PumaRacing 1]

Can we make a distinction between honing and glaze busting here? I suspect that what Puma, Mattsav PeterT etc are referring to is genuinely honing. Many people confuse this with glaze busting which produces a similar looking finish on a cylinder bore. A glaze buster is (usually) a three - pronged spring loaded tool which fits in an electric drill and produces an nice looking cross hatched finish in the bore.

 

That's also technically a hone but of the spring loaded brake cylinder type. Strictly speaking a glaze buster is either a flapwheel type affair or an abrasive brush with hundreds of round abrasive balls on nylon bristles. Proper hones for finishing bored blocks are made by Delapena, Sunnen, Snap-On and others. They have two abrasive stones and two wiper pads and a micrometer adjustment to wind them out to a fixed size. Getting them to work right is probably the hardest job in engine building. The speed, up and down feed, adjustment pressure, stone grit and honing fluid all have to be just right. Then you hit problems with cast iron blocks where the main bearing saddles are close to the bottom of the bores and you can't push the hone right through. You usually end up with the bore smaller at the bottom than the top in that case.

 

I've spent 15 years trying to perfect honing technique and it's still my least favourite job.

[Beastie 1]

That's also technically a hone but of the spring loaded brake cylinder type.

 

It's possible that I'm 20 years out of date with my terminology then - the old 3 pronged jobs once fell into the glaze buster category as opposed to "proper" hones from Messrs. Delapena etc. The abrasive brush type was originally made from wire before nylon was used but my battered brain can't think of the proper name for it.

 

It only occurred to me after my original post in this topic that it perhaps sounded as though I was criticising the measuring in increments of tenths. Skilled tradesmen have long worked reliably in tenths on the workshop floor. It was, however drummed into me often at college that I wasn't permitted to offer such tolerances as evidence if measured outside the laboratory Sorry if I wasn't clear!

[petert 554]

It was, however drummed into me often at college that I wasn't permitted to offer such tolerances as evidence if measured outside the laboratory Sorry if I wasn't clear!

 

It was drummed into me whilst doing my time in the Tool Room, not to quote measurements less than half of the graduation being measured. ie if your rule is in 1mm increments, the best you can measure to is half a mm. So all those who quote in tenths of a thou. from a micrometer...........

 

As for oversized pistons, I'm not game to go over 84mm with the Mi16 liner. The capacity increase for that is only approx. 50cc, so really no big deal. I think it's wiser to bore to 83.50mm if you want a custom piston and concentrate of deck height and compression ratio.

[Beastie 1]

It was drummed into me whilst doing my time in the Tool Room, not to quote measurements less than half of the graduation being measured. ie if your rule is in 1mm increments, the best you can measure to is half a mm. So all those who quote in tenths of a thou. from a micrometer...........

 

My bore gauge reads to 1 tenth of a thousandth of an inch

 

 

QED?

Edited February 28, 2006 by Beastie

[PumaRacing 1]

It was drummed into me whilst doing my time in the Tool Room, not to quote measurements less than half of the graduation being measured. ie if your rule is in 1mm increments, the best you can measure to is half a mm. So all those who quote in tenths of a thou. from a micrometer...........

 

What about micrometers with vernier scales reading tenths? Did the people in the toolroom think those could be read to half a tenth? I hope not. We used to hash this over every now and then in rec crafts metalworking on usenet. The accuracy and repeatability of measuring instruments isn't always a function of the graduations on their measuring scales. A good tool with a coarse scale might be capable of better resolution and a poor tool with a fine scale might not be capable of reading to its own scale. If I remember correctly the tenet in metrology is that a tool can only be calibrated accurately by another tool capable of accurately reading to one tenth of the resolution of the first tool.

 

A good mike calibrated in thou should be capable of reading to better than half a thou but the same mike with a tenths vernier scale is most unlikely to read or repeat accurately to a tenth. However accuracy and repeatability are not the same thing either. A mike might repeat very well but still not be accurate because of errors in its calibration or the accuracy of manufacture of its screw thread. Another might be very accurate but not repeat well because of stickiness in its thimble.

 

Most of my mikes have vernier scales but the best I'd say they repeat to is two or three tenths. Similarly my main bore gauge is marked in tenths but won't repeat to a tenth. Again two or three tenths is probably a realistic tolerance.

 

Temperature makes a massive difference when you're trying to read in tenths though. The heat that honing puts into a block can increase the bore size by half a thou or more and you can easily measure the change in bore size from summer to winter. 20 degrees C will change a 90mm cast iron bore by nearly a thou. When I'm trying to hone to very fine tolerances it usually takes me several days because I let the block stabilize after each honing for 12 hours before reading what size I'm up to. I also let the pistons stabilize in the same workshop and then transfer the skirt diameter from them to the bore gauge with the same mike.

[petert 554]

It's also the repeatability/accuracy of the user. The same mike, measuring the same thing, can be +/- half a thou., due to "feel".